Kiwix targets a website for off line presentation, it takes all the attributes of that website in order to show it as is.
When a website does not use web fonts like Wikipedia at the moment does, the result of the exercise will also be determined by the quality of the support for a script on the local host. This is often patchy.
When Wikipedia installations use WebFonts, it will use the fonts selected as default for a language. Some people will prefer a different font for reasons best known to them.
The use of fonts supplied with Kiwix is being considered at the moment. When they do, they may choose to adopt all the fonts collected to support Wikipedia as they will all be freely licensed.